Neuromodulatory actions of dopamine on synaptically-evoked neostriatal responses in slices

Abstract

7-OH-DPAT has been shown to exhibit selectivity between D2 and D3 dopamine receptors in a variety of in vitro assay systems. Although the drug has been used in a variety of studies to evaluate the behavioral effects of D3 receptor stimulation, the in vivo D2/D3 selectivity of the compound has not been determined. In this study, protection against inactivation by EEDQ was used as a measure of in vivo occupancy of D2 receptors by behaviorally relevant doses of 7-OH-DPAT (0.03-10 mg/kg, s.c.) in adult, male Sprague-Dawley rats. Ex vivo [3H]spiperone binding was then determined in striatal membranes. 7-OH-DPAT protected against inactivation of D2 receptors with an ED50 value of 11 mg/kg. Significant protection of D2 receptors was observed at doses of 1 mg/kg and above. These data suggest that stimulation of D2 receptors contributes to the pharmacological effects of 7-OH-DPat when administered at doses above 0.3 mg/kg (s.c.).